floating point - How to manage division of huge numbers in Python?

Question

I have a 100 digit number and I am trying to put all the digits of the number into a list, so that I can perform operations on them. To do this, I am using the following code:

for x in range (0, 1000):
   list[x] = number % 10
   number = number / 10

But the problem I am facing is that I am getting an overflow error something like too large number float/integer. I even tried using following alternative

number = int (number / 10)

How can I divide this huge number with the result back in integer type, that is no floats?

Answer 1

In Python 3, number / 10 will try to return a float. However, floating point values can't be of arbitrarily large size in Python and if number is large an OverflowError will be raised.

You can find the maximum that Python floating point values can take on your system using the sys module:

>>> import sys
>>> sys.float_info.max
1.7976931348623157e+308

To get around this limitation, instead use // to get an integer back from the division of the two integers:

number // 10

This will return the int floor value of number / 10 (it does not produce a float). Unlike floats, int values can be as large as you need them to be in Python 3 (within memory limits).

You can now divide the large numbers. For instance, in Python 3:

>>> 2**3000 / 10
OverflowError: integer division result too large for a float

>>> 2**3000 // 10
123023192216111717693155881327...